Identification of the Huntington’s gene by American geneticist Nancy Wexler in 1993 was instrumental in the development of a direct gene test for Huntington’s Disease. This test, called a pre-symptomatic test, can be used to predict Huntington’s Disease before symptoms develop.
Eligibility for the predictive test, according to international guidelines, are to be 18 years of age or above and to have a blood relative who has been diagnosed with Huntington’s Disease.
The predictive test is performed when a sample of blood is taken from the patient, DNA is then extracted from the blood cells and analysed for the expanded HTT gene.
Genetic testing is most informative and accurate when blood from an affected family member is also available.
Two procedures of pre-natal diagnosis for Huntington’s Disease are:
Amniocentesis, also called the amniotic fluid test, is a procedure in which amniotic fluid containing cells of the unborn child is collected with a needle, usually after the 14th week of pregnancy.
Collection of a sample from the chorionic villi, tissue of the placenta, can be done earlier, such as 11 weeks of pregnancy, but it is more risky to the unborn child.
There is a possibility of miscarriage with undergoing these tests.
Pre-implantation Genetic Diagnosis (PGD)
Pre-implantation Genetic Diagnosis (PGD), also known as embryo screening, is a diagnostic procedure combined with in vitro fertilisation (IVF); the embryos are screened for Huntington’s Disease prior to implantation.
PGD gives a couple the chance of conceiving a child that will not be affected by HD regardless of whether the prospective mother or father carries the expanded HTT gene.
In Tasmania testing is available through:
Tasmania Clinical Genetic Service
Royal Hobart Hospital
Box 1061 Hobart 7001